Breaker tool



Dec. 19, 1967 s, NQLEVY ET AL 3,359,038

BREAKER TOOL Filed Feb. 9, 1966 INVENTORSZ SYLVAN N. LEVY WILLIAM B. LEVY ATTYS.

United States Patent Ofiice 3,359,038 Patented Dec. 19, 1967 3,359,038 BREAKER TOOL Sylvan N. Levy, Hoekessin, and William B. Levy, Wilmington, Del., assignors to Delaware Tool Steel Corporation, Wilmington, Del., a corporation of Delaware Filed Feb. 9, 1966, Ser. No. 526,084 Claims. (Cl. 299-94) ABSTRACT OF THE DISCLOSURE A tool for use in breaking concrete paving, foundations, and similar masonry which may be sharpened after use without need for rehardening. The tool is elongated and has a cutting edge located in the normally-hardened marginal portion of the cross sectional area and indicia means, such as a groove or shoulder, is provided along the length of the tool to serve as a guide for maintaining the edge in the marginal portion after successive sharpenings.

The present invention relates to tools of the type used in conjunction with pneumatic, electric and gasoline hammers for masonry demolition purposes. The invention has particular application to tools used for breaking concrete paving, foundations and the like in the course of construction or repair.

Conventional tools of the stated type comprise moil points and chisels having broad cutting edges which are driven into the material which is to be broken up and removed. Tools of this character are normally forged and hardened by heat treating which hardens the outer marginal portion of the cross-sectional area of the tool, the central portion being relatively soft. This effect is particularly evident on shallow hardening tool steels which are used in applications of this type to obtain a material having combined shock and wear factors. As the tool is worn down and becomes dull, the standard practice is to redress the tool by reforging the same in order to reshape the point and thereafter rehardening and regrinding. Such redressing requires a skilled mechanic and is normally performed in a blacksmith establishment. During the redressing procedure, the working end of the tool is normally reshaped to provide a sharp taper adjacent the point which facilitates the wedging action of the tool and enables the same to be readily freed from the work material. Not infrequently the tools become lodged in the work material and the tool is broken when prying or hammering it loose.

With the foregoing in mind, the present invention provides a novel tool which eliminates or reduces the disadvantages of the conventional breaker tool and which is designed to be redressed or resharpened without the necessity for reforging, thereby enabling the tool to be resharpened in the field.

More specifially, the present invention provides a novel tool designed to have its cutting edge located in the outer marginal portion of the cross-sectional area thereof so that the tool may be repeatedly resharpened as it wears away without having the sharpened edge located in the softer central portion of the cross-sectional area.

In accordance with the invention, the tool may be resharpened in the field by a simple grinding operation and incorporates indicia means to facilitate the grinding so as to enable a relatively unskilled mechanic to perform a proper sharpening operation.

The shape of the working end of the tool is gradually tapered and terminates in a cutting edge olfset from the center line of the tool into the marginal area of the crosssection where the material is hardened, the gradual taper being somewhat arcuate so as to afford an inherent freeing action as the tool is used which reduces the binding or lodging of the tool in the work material.

All of the objects of the present invention are more fully set forth hereinafter with reference to the accompanying drawing, wherein:

'FIG. 1 is a View in side elevation of a tool embodying the present invention;

FIG. 2 is an enlarged plan view of the working end of the tool shown in FIG. 1 at an enlarged scale, broken away at two levels to illustrate the structural characteristics thereof;

FIG. 3 is a View in side elevation of the working endof the tool shown in FIG. 2 with a portion broken away;

FIG. 4 is a fragmentary perspective view of the working end of the tool with a portion broken away;

FIG. 5 is an end elevational view at an enlarged scale as seen from the right in FIG. 1;

FIG. 6 is. a view similar to FIG. 4 showing a modified embodiment of a breaker tool in accordance with the present invention; and

FIG. 7 is a view similar to FIG. 5 showing the tool of FIG. 6 in end elevation.

Referring now to the drawing, and more particularly to the embodiment of the invention shown in FIGS. Ho 5 inclusive, the tool comprises a central body portion 11, which in the illustrated form is of circular cross-section, having at one end a hexagonal shank 12 terminating at its inward end in a collar 13 for mounting the tool in the operating hammer. At its other end, the body portion 11 is formed as a working bit 15 which is of generally rectangular cross-section having a flat upper surface 16 arranged tangential to the body portion 11 at its junction therewith and is longitudinally aligned substantially parallel to the central longitudinal axis of the tool. The bottom surface of the working end 15 is of flat arcuate form having a width substantially equal to the width of the top surface 1 6. At its junction with the body portion 11, the flat bottom surface 17 is tangential to the body portion and extends toward the tip of the tool in a gentle arc converging toward the upper surface 16 beyond the central longitudinal axis of the tool. At the tip of the working bit 15, the upper surface 16 terminates in a bevel 18 which meets a corresponding bevel 19 of the bottom surface '17 in a cutting edge 26 disposed in the upper marginal portion of the tool cross-section. The side surfaces 23 and 24 of theworking end 15 are flat and perpendicular to the topand bottom surfaces 16 and 17. In the present instance, the surfaces 23 and 24 are parallel to one another, but it-rnay be found desirable for many applications to taper the working end by tapering the sides towards the cutting edge, for example from a width of one inch adjacent the body portion 11 to a Width of /8 inch at the cutting edge Zilr.

In accordance with the invention, the tool is provided with indicia extending rearwardly from the cutting edge 20 parallel to the upper surface 16. In the embodiment of FIGS. 1 to 5, the indicia comprise recesses 25 and 26 formed in the side walls 23 and 24 as grooves which provide a shoulder for a purpose more fully set forth hereinafter.

In the manufacture of this tool, the tool is formed in the shape described and is then dressed which includes hardening at least the Working bit of the tool. Particularly, on shallow hardening tool steels, the hardening process hardens the material to the maximum degree on the outer margin of the cross-section, and the material tapers oflf in degree of hardness towards the center. Thus, after the hardening process, the central core of the tool is softer, as indicated by the stippling at 29 in FIGS. 2, 3, and 4, leaving the outer marginal portion of the cross-sectional area of the tool relatively hard. As shown, the cutting edge 20 is located in the hardened outer marginal portion of the cross-sectional area of the tool, and when the beveled surfaces 18 and 19 are ground to provide the sharpened cutting edge 20, the entire cutting edge is located in the hardened area.

As the tool is used, the edge 20 becomes dull and practice with previous conventional tools required the tool to be returned to a blacksmith establishment for reforging, rehardening, and grinding. With the tool of the present invention, the tool need not be reforged and rehardened but need only be reground to reinstate a sharpened cutting edge. The regrinding process, as the tool is used, shortens the length of the working end 15 of the tool, but because of the location of the cutting edge in the outer marginal portion of the cross-section of the tool, the cuting edge as it progresses toward the collar 13 remains in the hardened marginal portion of the tool and eliminates the need for rehardening. The indicia provided by the recesses 25 and 26 enable a relatively unskilled mechanic in the field to properly locate the cutting edge 20 in the hardened marginal portion of the cross-section of the tool. As the cutting edge recedes during repeated use, to be sure, the beveled surface 19 of the lower surface 17 progresses into the relatively soft core area 29 of the crosssection although the cutting edge 20 remains in the relatively hard section. This does not deleteriously affect the functional efficiency of the tool since the cutting edge is the prime working portion of the working end 15 of the tool.

Although the gradual convergence of the lower surface 17 toward the upper surface 16 reduces the wedging action normally associated with conventional tools of the stated type, it has been found that the fact that the cutting edge 20 is offset from the central axis of the tool induces lateral vibrations as the tool is used which keep the working end moving freely, preventing it from binding in the work material. It is believed that the shoulders provided by the recesses 25 and 26 also contribute to the lack of binding or lodging of the tool in the work material. The gentle arcuate form of the lower surface 17 further resists binding since it serves as a rocking fulcrum on which the tool is rocked in order to pry out chunks of the material as they become loosened from the mass. Thus, it has been found that in addition to the efliciency attained by the elimination of the need for returning the tool to a blacksmith establishment for sharpening and redressing, the elficiency in actual operation of the tool is increased over the conventional tool of this character.

The indicia means may take forms other than the grooves 25 and 26. For example, in the tool shown in FIGS. 6 and 7, the tool is similar to the tool shown in FIGS. 1 to inclusive including a body portion 41, in the present instance circular, having a shank and collar 43 at one end and a working bit 45 at the other end. The working end 45 has upper and lower surfaces 46 and 47, respectively terminating at the tip in beveled surfaces 48 and 47, respectively terminating at the tip in beveled surfaces 48 and 49 which meet to form a cutting edge 50. The side surfaces 53 and 54 are provided with indicia means in the form of recesses 55 and 56, respectively, which are aligned above the softer central core 59 of the working end of the tool. The recesses 55 and 56 form shoulders between which the cutting edge 50 is formed as the tool is successively ground down for sharpening. The form of the recesses 55 and 56 provides two sharp corners or shoulders at each side of the fiat upper surface 46 which are believed to contribute to the efficient functioning of the tool as it is used. The tool of FIGS. 6 and 7 is possessed of the advantages of the previously described tool and constitutes an effective work piece in accordance with the invention.

While particular embodiments of the present invention have been herein illustrated and described, it is not intended to limit the invention to such disclosure, but changes and modifications may be made therein and thereto within the scope of the following claims.

We claim:

1. A tool for masonry demolition comprising an elongated body portion having a shank at one end and a working bit at the other end, said working bit being of generally rectangular cross-section and having a flat upper surface disposed substantially parallel to the central longitudinal axis of the tool; an arcuate bottom surface corresponding in Width to said upper surface and converging gradually toward said upper surface; and substantially fiat side surfaces substantially perpendicular to said top and bottom surfaces; said top and bottom surfaces terminating in beveled portions which meet in a cutting edge, said cutting edge disposed parallel to said upper surface and being positioned in the outer marginal portion of the crosssection of said tool; said tool being hardened to a maximum degree in the marginal portion of its cross-section surrounding the softer central core thereof whereby said cutting edge is'disposed in said hardened portion of the tool; said side surfaces of the working end of the tool being provided with indicia means defining lines extending parallel to said upper surface rearwardly from said cutting edge on said side surfaces.

2. A tool according to claim 1 wherein said indicia means comprises shoulder means.

3. A tool according to claim 2 wherein said shoulder means is formed by grooved recesses formed in said side surfaces in closely-spaced parallel relation to said upper surface.

4. A tool according to claim 2 wherein said shoulder means is formed by angular recesses formed in said working end at the junctions of said upper surface with said side surfaces.

5. A tool for masonry demolition comprising an elongated body portion having a shank at one end and a working bit at the other end, said working bit having a flat upper surface disposed substantially parallel to the central longitudinal axis of the tool; an arcuate bottom surface converging gradually toward said upper surface; and side surfaces; said top and bottom surfaces terminating in beveled portions which meet in a cutting edge positioned in the outer marginal portion of the cross-section of said tool; said tool being hardened to a maximum degree in the marginal portion of its cross-section surrounding the softer central core thereof whereby said cutting edge is disposed in said hardened portion of the tool; said side surfaces of the working end of the tool being provided with indicia means defining lines extending parallel to said upper surface rearwardly from said cutting edge on said side surfaces.

6. A tool according to claim 5 wherein said upper surface is of substantially uniform width throughout its length, and said lower surface and said cutting edge are at least as wide as said upper surface.

7. A tool according to claim 5 wherein said indicia means comprises shoulders formed by grooved recesses formed in said side surfaces in closely-spaced parallel relation to said upper surface.

8. A tool according to claim 5 wherein said indicia com- 7 prises shoulders formed by angular recesses formed in said working end at the junctions of said upper surface with said side surfaces.

9. A tool according to claim 5 wherein said side surfaces are substantially flat and parallel to one another and perpendicular to the top and bottom surfaces, whereby said top and bottom surfaces are of uniform width throughout their length and said cutting edge is equal in width to said surfaces.

10. A tool according to claim 5 wherein said side surfaces are substantially flat and perpendicular to the top and bottom surfaces, said bottom surface being at least as Wide as said top surface and said cutting edge.

References Cited UNITED STATES PATENTS Armbruster 30--168 Shaughency 29994 Gairoard 175398 Gardner 29994 X 10 ERNEST R. PURSER, Primary Examiner. 

5. A TOOL FOR MASONRY DEMOLITION COMPRISING AN ELONGATED BODY PORTION HAVING A SHANK AT ONE END AND A WORKING BIT AT THE OTHER END, SAID WORKING BIT A FLAT UPPER SUFACE DISPOSED SUBTANTIALLY PARALLEL TO THE CENTRAL LONGITUDINAL AXIS OF THE TOOL; AN ARCUATE BOTTOM SURFACE CONVERGING GRADUALLY TOWARD SAID UPPER SUFACE; AND SIDE SURFACES; SAID TOP AND BOTTOM SURFACES TERMINATING IN BEVELED PORTIONS WHICH MEET IN A CUTTING EDGE POSITIONED IN THE OUTER MARGINAL PORTION OF THE CROSS-SECTION OF SAID TOOL; SAID TOOL BEING HARDENED TO A MAXIMUM DEGREE IN THE MARGINAL PORTION OF ITS CROSS-SECTION SURROUNDING THE SOFTER CENTRAL CORE THEREOF WHEREBY SAID CUTTING EDGE IS DISPOSED IN SAID HARDENED PORTION OF THE TOOL; SAID SIDE SURFACES OF THE WORKING END OF THE TOOL BEING PROVIDED WITH INDICIA MEANS DEFINIGN LINES EXTENDING PARALLEL TO SAID UPPER SURFACE REARWARDLY FROM SAID CUTTING EDGE OF SAID SIDE SURFACES. 